Download Fly Notation

Fly Notation and Linked
Genes
Thomas Hunt Morgan
• Found that specific genes are carried on
specific chromosomes
• Drosophila melanogaster – fruit fly
• Fast breeding, 4 pairs of chromosomes (XX/XY)
Drosophila Notation
• Typical (normal) appearance = “wild type”
• The mutation decides the allele symbol
• Normal/wild type body color = gray
• Mutant body color = black
So…
• Gray (wild type) is bl+ and ebony (mutant) is bl
Drosophila Notation
• Cross a heterozygous gray fly with a homozygous black fly
(recessive trait). What ratio of colors do you expect in the
progeny?
Drosophila Notation
• The allele symbol is lowercase if it is inherited
in a recessive pattern
• Gray (wild type) bl+ and ebony (black) is bl
• The allele symbol is capital if it is inherited in a
dominant pattern.
• Wild type eye shape is round, B+
• “Bar eye” (a narrow eye) is a mutation, B
Drosophila Notation
• Cross a normal-eye fly with a heterozygous bar-eye fly. What
ratio of eye shape do you expect in the progeny?
Drosophila Notation
• Normal wings = wild-type
• Vestigial wings (small) = mutant, recessive
• If a homozygous wild type fly is crossed with a
homozygous vestigial fly, how many flies in the F1
generation will have vestigial wings?
• If two flies from the F1 generation are crossed with
each other, how many will have vestigial wings in the
F2 generation?
Male vs. Female Flies